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Axial magma reservoirs located by variation in lava chemistry along Iceland's mid-ocean ridge

Axial magma reservoirs located by variation in lava chemistry along Iceland's mid-ocean ridge
Axial magma reservoirs located by variation in lava chemistry along Iceland's mid-ocean ridge
A linear, axis-parallel, array of glacial and postglacial basalt samples from the elevated mid-ocean ridge in southwest Iceland, the Reykjanes Peninsula, shows three MgO lows and two MgO highs at 40 km intervals. Similar patterns are observed with other fractionation indices, e.g., Cr. These along-axis variations in elements affected by fractional crystallization are interpreted as evidence for segment-scale variation in crustal residence times arising from the focusing of magmatic activity at regular intervals along this elevated mid-ocean ridge. In the majority of the samples, Nb/Zr, generally considered to be unaffected by crystal fractionation, does not show a systematic variation with MgO. Lavas with unusually low Nb/Zr, erupted at the end of the last glaciation, are the only exception. These low-Nb/Zr lavas are generally restricted to the MgO highs, resulting in a wider range of lava Nb/Zr in these areas than in the MgO lows. It is proposed that low-Nb/Zr melts are available along the entire ridge section at all times, but are modified before eruption by mixing with melts that are more enriched in incompatible elements. Crustal processes at this ridge axis are governing the distribution of chemistry associated with the mantle.
MID OCEAN RIDGES, ICELAND, MAGMA, LAVA, GEOCHEMISTRY
0091-7613
699-702
Gee, M.A.M.
4106eadc-6aa5-48fb-88cb-606eb307e3da
Taylor, R.N.
094be7fd-ef61-4acd-a795-7daba2bc6183
Thirlwall, M.F.
eef507cc-401b-4d16-bccf-953c37509e7e
Murton, B.J.
9076d07f-a3c1-4f90-a5d5-99b27fe2cb12
Gee, M.A.M.
4106eadc-6aa5-48fb-88cb-606eb307e3da
Taylor, R.N.
094be7fd-ef61-4acd-a795-7daba2bc6183
Thirlwall, M.F.
eef507cc-401b-4d16-bccf-953c37509e7e
Murton, B.J.
9076d07f-a3c1-4f90-a5d5-99b27fe2cb12

Gee, M.A.M., Taylor, R.N., Thirlwall, M.F. and Murton, B.J. (2000) Axial magma reservoirs located by variation in lava chemistry along Iceland's mid-ocean ridge. Geology, 28 (8), 699-702. (doi:10.1130/0091-7613(2000)28<699:AMRLBV>2.0.CO;2).

Record type: Article

Abstract

A linear, axis-parallel, array of glacial and postglacial basalt samples from the elevated mid-ocean ridge in southwest Iceland, the Reykjanes Peninsula, shows three MgO lows and two MgO highs at 40 km intervals. Similar patterns are observed with other fractionation indices, e.g., Cr. These along-axis variations in elements affected by fractional crystallization are interpreted as evidence for segment-scale variation in crustal residence times arising from the focusing of magmatic activity at regular intervals along this elevated mid-ocean ridge. In the majority of the samples, Nb/Zr, generally considered to be unaffected by crystal fractionation, does not show a systematic variation with MgO. Lavas with unusually low Nb/Zr, erupted at the end of the last glaciation, are the only exception. These low-Nb/Zr lavas are generally restricted to the MgO highs, resulting in a wider range of lava Nb/Zr in these areas than in the MgO lows. It is proposed that low-Nb/Zr melts are available along the entire ridge section at all times, but are modified before eruption by mixing with melts that are more enriched in incompatible elements. Crustal processes at this ridge axis are governing the distribution of chemistry associated with the mantle.

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More information

Published date: 2000
Keywords: MID OCEAN RIDGES, ICELAND, MAGMA, LAVA, GEOCHEMISTRY

Identifiers

Local EPrints ID: 8710
URI: https://eprints.soton.ac.uk/id/eprint/8710
ISSN: 0091-7613
PURE UUID: b1e86cdb-e9e2-478f-8798-563e99ba5ce6

Catalogue record

Date deposited: 25 Aug 2004
Last modified: 17 Jul 2017 17:12

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